Preoccupied engineer started cab (10)
I believe the answer is:
abstracted
'preoccupied' is the definition.
(synonyms)
'engineer started cab' is the wordplay.
'engineer' is an anagram indicator.
'started'+'cab'='startedcab'
'startedcab' anagrammed gives 'ABSTRACTED'.
(Other definitions for abstracted that I've seen before include "Taken out" , "without concentrating" , "Removed - preoccupied - absent-minded" , "miles away" , "not paying attention" .)